Febdinand porsche



rtent d'o t. 11, 1927.

Lem

UNITED S-TATTES *PATENT OFFICE.

IEBDINAND ronsonn, or STUTTGA T-UNTERTURKHEIM, GERMANY, ASSIGNOR, :BY 'MESANE assremmnms, 'ro nammmnnnz AKTIENGESELLSCHAFT, or BEn m, GER- MARY FL'UID-PRESSUBE BRAKE FOR POWER-DRIVER' ROAD VEHICLES.

Application filed January 18, 1926, Serial No. 81,824, and in Austria August 8, 1823.

This invention oomprises improvements 'in and connected with brake meohanisms forvehicles and articularly motor road vehicles. In 'ord er to simplify these mechanisms and to avoid rod 'and link transmissions, ithas already been proposed to adopt hydraulio and pneumatic transmissions'for the brakes of motor road vehicles, and .such proposals have been made more particularly in connection'with four .wheel brakingL In spite of the advantages'to be obtained with brake mechanisms of this description, they have been found to be far from perfect, mainly owing to the .fact that there is no 5 absolute guarantee that the wheels cannot become looked by ex'oessive brake pressure. As is well-known, the looking of the wheels,

and especially the front wheels, of a motor road vehicle is liable to have serious 'consequenoes and may result in aocidents due to the skidding or overturning of the vehiole.

The looking of the wheels by any brakes may be due to want of skill or attention on the part of the driver who may inadvertent- 'ly make a too sudden ap lication of the brakes. However, it is not ue to this alone as the danger of looking is inherent to the meohanical construotion and method of operation. Looking of wheels always takes place when the braking moment and the adheson of the wheels on the ground are equal. ,The coeflioient of friction between the brakedrum and the brake shoes or de-` vice increases to a substantial extent with decrease of 'speed whereas the coeficient of friotion between the' road surface and the tyres changes only to a very slight extent with change in speed; consequently the great 'pressure applied at the beginning of 40 a brakng operaton must be reduced as the speed decre'ases if looking of the wheels .is to be avoided. Ordinary'brake mechanisms, however, operate just in the reverse sense and, owing to this characteristic, it is very diflioult for the driver even withthe exercise of wheels. Apart from the danger of looking the wheels expla ined above there isthe further great care, to avoid looking the 0 danger that oIe or 'other-of the wheels may .become locked owing, for example, to a ,change in the condition of the 'individual friction surfaces whereby the braking action on one wheel might be greater than on another and suflicient for causing thatwheel to lock. In such cases, the driver is powerless to do anything to prevent looking from ocourring.

The prinoipal object of the present inven ton s to devise hydraulic and pneumatic brakeinstallations adapted for meetn all requirements and for ensuring, in a relable manner, the avoidance of wheel-looking, either as regards individualwheels or all the wheels of a vehiole. v

According to this invention, relative movement taking place between parts of the vehiole, and due to the braking action being opposed to momentum, is caused to influence the brake meohanism in such a manner as to reduce the braking action at the instant when it may reach the value at which looking of the wheels may take place. The reduction of brake pressure brought about in this `manner preoludes looking of the wheels in all circumstances. The forces of momentum will always become active for producing the said relative motion when op ed to the forces due to the resistance o ered by ground contact, no matter what ma be the condition of the road or the spee of the vehiole, so that the looking ofwheels by the brakes is reliably avoided in a perfectly automatic manner. s

In carrying out the invention, a spring or equivalent devioe is introduoed' between braked and non-braked vehiole parts and an i adjustment is provided for enabling the resistanoe of the spring or equivalent devioe in the manner aforesaid when the vehiole speed is reduced to "such a point that there may be danger of wheel looking. Upon further retardation, the speed is reduced still .further so that there may be again a danger' of wheel-looking, whereupon the automatic and to means again functions for further reducing be utilized for altering a fluid pressure employed in the transmission.

In the' accompanying drawing two constructional examples of the invention are shown diagrammatically.

Fig. 1 illustrates a brake operated by hydraulic means. v

Fig. 2 a brake with means for Operating it by compressed air, and

Fi 3 is a sectional detail of the cylinder on t e chassis showing particularly the adjustin means for the spring.

Accor ing to Fig. 1 in the brake drum a of the road wheel b brake blocks c are mounted in the ordinary way. The brake blocks are applied by means of a wedge dmounted on a plunger e which is adapted to slidein a cylinder f containing liquid. The cylinder f is in communication with a cylinder 72,' through the pipe g. To the piston i of the cylinder h is attached a small rod Ic which is pivotally connected to one arm l of a double armed lever pivoted at the point m. At a point on the other arm of this lever is pivoted a rod 0, the other end of which engages in the slotted arm p of the foot operated lever g. To the end 7' of the same arm of the double armed lever' is pivotally attached a small rod 8, which acts on a pisten' t in the liquid cylinder u. This latter cylinder may be suitably connected to the brakes of the other pair of road wheels, not shown. The rod 0 is in engagement with the arm w of a crankedlever v, w, pivoted'at a dpoint rigid with the chassis while to the en of the other arm v a connecting rod a: is pivpted. The rod m is preferably oonstructed in sections'which are pivoted to one ofthe shackles of the front supporting spring. The connection' between the front section of the rod m and the frame y consists for instance of a piston z in a cylinder 1 and a spring 2 pressing against the (pisten. The tenson of the spring may be a justed y the adjustable end plate a' of the cyliner. I

The device works as follows A The pressure 'exerted by the driver on the foot operated lever g is transmitted through the slotted lever p, the rod o, the pivoted cranked lever n, m, Z, the rod k and the piston ito the liquid in the cylinder IL. By this means the piston e in the cylinder f is displaced and the wedge d forces the brake blocks against the brake drum; In order that the wheels shall not become locked, the braking pressure is, when necessary, auto matically diminished to a suitable extent shortly before such looking would occur, owing to the connection z, 1, 2 between the frame and the parts of the vehicle acted on by the brake. Through this connection each time at the moment, in which the road surface resistance of the wheels produced by the braking almost reaches the possible adhesive moment, the nohbraked parts of the vehicle, owing to their momentum, will move forward with respect to braked parts 'of the vehicle, since the road. surface resistance acts as a tensile force in opposition to the inertia of the non-braked parts of the vehicle.

For this purpose the spring 2 used in the constructional example shown in the drawing is so adjusted as to give when the maximum permissible tensional force is reached. The rod 'n and the cranked lever o, w wil thereby move the rod'o for instance out of the position shown in full lines into that shown in dot and dash lines, thus reducing the ratio of transmission between the pedal and the slotted lever Z, which causes a diminution in the pressure acting in the cylinder h. Consequently with the arrangement according to the invention no looking of the wheels can take place. In every case, however, the most efiective action of the brake, which takes place just before the looking of the wheels, is brought about independently of the skill of the driver by the automatic regulation of the pressure with which the brakes are applied.

In the constructional example shown ir Fig. 2 the brake instead of being operated hydraulically is operated by pneumatic means. In the example shown the arrangement consists of a compressed air reservoir 3 which may be supplied from a compressor,

not shown in the drawing. The reservoi" is provided with a valve 4: which is adjusted by any suitable means. 5. In the pipe 6 connecting the pressure cylinder 7 to the reservoir 3 is a regulating member 8. This member may consist of a blow-off valve which 19 operated by the sectional rod 9 pivoted to one of the spring shackles and to a cranked lever 10, 11' pivoted in turn to the chasss. 'At one end of the sectional rod 9 is a piston '10 which slides in a cylinder'12 fixed to the frame 11 and 'is loaded for instance by a spring 13. To the pipe 6 is connected another pipe' 14: which leads to the brakes of the other road wheels of the vehicle, not shown in the drawing.

This arra'ngement operates in principle 'sim'il'arly to that shown in Fig. 1. In contradistincton to the arrangement shown in h Fig. 1 the pressure is not varied by varyi-ng the leverages, but by. opening and closing the valve 8. This arrangement forms a sina plification of 'that shown 'inF-ig. 1.

The connection of the pneumatic brake with the pressure regulating means described is of particular importance for brakes of this knd, as the operation of pneumativ brakes is almost entirely independent of the feet of the drverm Hence with brakes of this t pe without 'the pressure regulation accor mg to the invention the danger of the wheels becoming locked is far greater than 'The `arrangement-may, however, be proi Vided only for the front wheels or only for the back wheels.

'A point, on which particular stress should be laid, is that the invention enables the braking pressure on each separate wheel to be `regulated with certainty' and always at the right time. This is only made possible bythe road surface resistance being utilized for the regulation. With the known types of brakes the driver, even by exercising the greatest attention, cannot prevent for instance one wheel becoming locked owing tounequal `tensional forces.

'I claim: v

1. In a' power driven vehicle, the combination with non-braked elements, braked elements including the road wheels, said non-brakedelements .being 'capable of displacement relatively to said brakedelements, brakes for the road wheels of the vehicle and mechanism for applying the i brakes to the road wheels, said mechansm .comprising means for transmtting the braking ,force by fluid pressure,' of means intended to cooperate With the non-braked elements and the braked elements so as to be actuable by said displacement for limiting the braking pressure.

Ition With non-brakedelements, braked ele- 2. In a power driven vehicle, the combinaments including the road wheels, said nonbraked elements being capable of displacement relatively to saidi braked elements, brakes for the road wheels of the vehicle and mechanism for applying 'the brakes to the-road wheels, said mechanismtomprising means for transmitting the^braking force by fluid pressure, of means intended by said displacement for limiting the braku to cooperate with the non-braked elements and the braked elements so as to be actuable -tion with non-braked ing pressure of the brakes of the road wheels of one axle. i r

3. In a power dri en vehicle, the combina tion with non-braked elements, braked ele- .-ments including the road wheels, said nonbraked elements being capable of displacement relatively to said braked elements', brakes for the road wheels of the vehicle and mecha-nism for applying the 'brakes to the road wheels, said mechanism com risi11g` means for transmitting the bra ing force 'by fluid -pressure, of means intended to cooperate wth the non-braked elements 'andthe braked elements so as to be actuable by said displacement for limiting the braking pressure of the brakes of all the road wheels.

4. In' a power driven vehicle, the combinaelements, elements including the road wheels, said non-braked' elements being capable of displacement relatively to -said braked elements, brakes for the road wheels of the vehicle and mechanism: for applying the brakes to the ,road wheels, said meehanism conprising 'means 'fo-r transmitting the braking force by fluid pressure, of means intended to cooperate with the non-braked elements and the braked elements so as to braked ments including the road wheels,`said nonbraked elements being capable of displacement relatively to said braked elements; brakes for the road wheels of the vehicle and mechanism for 'applying the brakes to the road wheels, said 'mechanism comprising means for transmitting the braking force by fluid pressure, of means intended to cooperate with the non-braked elements and the braked elements so as to be` actuable' by I said displacement for limiting the braking pressure and adjustable meansfor opposing a yielding resistance to the displacement of the'non-braked elements with respect to..the

braked elements. i 4 6. In a power driven vehicle, the combination with non-braked elements, braked elementsincluding the road wheels, said nonbraked elements being capable of displacement relatively to .said braked elements,- brakes for the road wheels of. the vehicle and mechanism for .applying thebrakes to the road wheels, said mechanism comprising means for transmitting the braking 'force by fluid pressure, ofmeans intended to co-operate with the non-braked elements and the braked elementss o as to be actu'able by said 'displacement 'for limiti'ngthe braking pr'essure and a bufler spring 'for opposing a yielding resist-ance to the` dsplacement of the non-braked elements with respect to the braked elements.

7. In a power driven vehicle, the combination with non-braked elements, braked elements including the road wheels, said nonbraked elements being capable of displacement relatively to said braked elements, brakes for the road wheels of the vehicle and mechanism for applying the brakes to the road wheels, said mechanism comprising means fort-ransmitting the braking force by fluid pressure, of means intended to cooperate with the non-braked elements and the braked elements so as to be actuable by said displacement for limiting the braking pressure and an adjustable bufler spring for opposing a yielding resistance to the displacement of the non-brak'ed elements with respect to the braked elements. 7

' 8. In a power driven vehile, the combination with non-braked elements, braked elements including the road wheels, said nonbraked elements being capable of displace- -ment relatively to said braked elements,

brakes for the road wheels of thevehicle and mechanism for applying the brakes to the road wheels, said mechanism comprising means for transmitting the braking force by fluid pressure, of means intended to cooperate with the non-braked elements and the braked elements so as to be aetuable by said displacement for limiting the braking pressure, an adjustable bufi'er spring for oppos-- ing a yielding resi'stance to the displacemeit of the non-braked elements with respect to the braked elements and means controllable by the bufer spring for reducing the leverage of the brake applyng mechanism and thereby reducing the braking pressure.

9. In a power driven vehicle, the combinetion with non-braked elements, braked elements including the road wheels, said nonhraked elements being capable of displacement relatively to said braked elements, brakes for the road wheels of the vehicle, a

brake applying member, mechanism for' applying the brakes to the road wheels, said mechanism comprising means for transmitting the braking force by fluid pressure, a

' bra'ke rod having a variable point of application interposed between said brake applyingmember and said brake applying mechanisin, an adjustable bufl'er spring for opposing a yielding resistance to the displacement of the non-braked elements with respect to the braked elements and means connected to said buffer spring for varying the point of application of the brake rod. In testimony whereof I name to this sgecification.

- ERDINAND PQRSCHE.

have signed my. 

